Accumulator piston for use in vehicle transmission system

ABSTRACT

An accumulator piston configured to be situated within an accumulator bore of a housing for use in vehicle transmissions. The accumulator piston including a casing, the casing including a top surface, a bottom surface opposite the top surface, and a side wall situated between the top surface and the bottom surface, a pin guide protruding from the top surface of the casing, the pin guide including a centrally disposed aperture, the aperture configured to receive an elongated pin, and a sealing member encircling the side wall of the casing such that the sealing member covers any exposed surface of the side wall.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/556,487, filed on Aug. 30, 2019, the contents of which are herebyincorporated by reference.

TECHNICAL FIELD

This disclosure relates to accumulator pistons for use in vehicles andmore specifically to an accumulator piston having a bi-directional lipseal around the outer perimeter of the accumulator piston to provideimproved lateral support.

BACKGROUND

Vehicle transmissions, particularly automatic vehicle transmissionsinclude both mechanical and hydraulic subsystems. The hydraulicsubsystem actuates clutches in order to change the transmission gearspeed ratio based on a controller signal.

Included in the hydraulic subsystem are accumulators. Accumulators areused to dampen the harshness of a shift in a transmission by slowing oraccumulating the pressure rise in the application circuit of a clutchpack or band. In other words, the accumulator acts as a modifier thataffects transmission shift timing and quality. Accumulators absorb theinitial shock of pressure changes in the hydraulic circuit. When aclutch or band's piston or servo first strokes, there is low pressure inthe circuit. As soon as the piston or servo starts to apply, pressureincreases rapidly. Without a shift modifying device like an accumulator,sudden and harsh shifting is likely to occur.

Accumulators are designed to “cushion” or “dampen” a shift by slowingdown the apply oil to a clutch pack or a band. Accumulators may overcomespring force, or hydraulic fluid during a shift event to provide this“cushion” or “dampening” effect.

In typical prior art accumulators, the accumulator is made of aluminumand is guided through its stroke by a steel pin through the center ofthe accumulator piston. The piston is sealed and supported on theoutside diameter by a single lathe cut rubber type seal, or a singlepolytetrafluroethylene (PTFE) sealing ring. Often times, accumulatorscan leak due to such things as a worn seal, worn bore or worn centeringpin. Further, a single seal provides inadequate lateral support thatallows the piston to rock in the bore on apply and release. Thiscontinual rocking creates wear to the pin bore and/or seal, and, inextreme cases, damages the accumulator bore. This wear creates a leak inthe accumulator hydraulic circuit and can contribute to slipping of thebrake band, and or the slipping or burning of the clutch pack.

Thus, there is a need for an accumulator piston design that does notresult in wear or damage to the accumulator bore or pin bore. Thepresent disclosure addresses this need.

SUMMARY

In one embodiment, the accumulator piston of the present disclosure isconfigured to be situated within an accumulator bore of a housing. Inone aspect, the accumulator piston includes a casing, the casingincluding a top surface, a bottom surface opposite the top surface, anda side wall situated between the top surface and the bottom surface. Theaccumulator piston also includes a pin guide protruding from the topsurface of the casing, the pin guide including a centrally disposedbore, the bore configured to receive an elongated pin, and a sealingmember encircling the side wall of the casing such that the sealingmember covers any exposed surface of the side wall.

In another embodiment, the accumulator piston of the present disclosureis configured to be situated within an accumulator bore of a housing foruse in automatic vehicle transmissions. In one aspect, the accumulatorpiston includes a cylindrical casing, the cylindrical casing including atop surface, a bottom surface opposite the top surface, and a side wallsituated between the top surface and the bottom surface. The accumulatorpiston also includes a pin guide protruding from the top surface of thecylindrical casing, the pin guide including a centrally disposed bore,the bore configured to receive an elongated pin. The accumulator pistonalso includes a polymer sealing member encircling the side wall of thecylindrical casing such that the sealing member covers any exposedsurface of the side wall, the sealing member providing a uniform surfacesuch that the sealing member is configured to prevent misalignment ofthe accumulator piston within the accumulator bore by maintaining thecylindrical casing in a substantially parallel orientation with respectto the accumulator bore.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a top view of an accumulator piston in accordance with theprinciples of the present disclosure;

FIG. 2 is a bottom view of the accumulator piston in accordance with theprinciples of the present disclosure;

FIG. 3 is a side perspective view of the accumulator piston inaccordance with the principles of the present disclosure;

FIG. 4 is a side view of the accumulator piston in accordance with theprinciples of the present disclosure;

FIG. 5 is a cross-sectional view of the accumulator piston in accordancewith the principles of the present disclosure;

FIG. 6 is another cross-sectional view of the accumulator piston inaccordance with the principles of the present disclosure, showing thecasing and seal interface in greater detail;

FIG. 7 is a top, perspective view showing the accumulator pistoninserted within a housing in an inverted position; and

FIG. 8 is a top, perspective view showing the accumulator pistoninserted within the housing in an un-inverted view.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present disclosure provides a novel accumulator piston for use in ahousing of a vehicle's transmission system. The housing could be, forexample, an accumulator housing, or a transmission case or housing.Thus, the term “housing” as used herein shall not be limited in any wayand instead be broadly construed to include an accumulator housing, atransmission case, or any other type of housing that may be used toreceive and house an accumulator piston. Referring now to the figures,FIG. 1 illustrates a top view of an accumulator piston 10 in accordancewith the principles of the present disclosure. Accumulator piston 10 iscomprised of a cylindrical casing 12, the casing 12 having a top surface14, a bottom surface 16 (shown in FIG. 2), and a side wall 18.Accumulator piston 10 is sized such that it can be incorporated within ahousing (shown in FIGS. 7 and 8) of a vehicle's transmission system, forexample, an automatic transmission system. Accumulator piston 10 acts asa shock absorber for the hydraulic subsystem. The accumulator piston 10is used to dampen the shift of the transmission by slowing oraccumulating the line rise in the application circuit of a clutch packor band.

Protruding from the substantial center of top surface 14 of casing 12 isa pin guide 20, which includes a centrally disposed aperture 22.Aperture 22 is configured to receive an elongated accumulator pin thatguides the accumulator piston 10 within the housing. Pin guide 20 can beformed separately and joined to the top surface 14 of casing 12, or canbe an integral part of and incorporated into the top surface 14 ofcasing 12. In one embodiment, at least one of the pin guide 20 and theelongated pin inserted therein, is made of hardened steel.

To avoid the aforementioned problems associated with a piston rockingwithin the piston bore of the housing, the accumulator piston 10 of thepresent disclosure includes a sealing member 24 disposed around theperiphery, i.e., the side wall 18 of cylindrical casing 12. As shown inFIG. 1 (and FIG. 2), sealing member 24 is a dual-lip seal thatsubstantially covers the entirety of the exposed surface of side wall 18of casing 12. Thus, sealing member 24 is not merely a narrow band thatcovers a portion of the side wall 18 of casing 12 or resides within agroove of casing 12, but instead is a dual-lip design that covers theside wall 18 and also extends over and beneath the side wall 18, i.e.,thus covering more than just side wall 18 of casing 12. This is shown inFIG. 3 and discussed below.

In one embodiment, sealing member 24 is made from a polymer material,and in non-limiting embodiments, can be made of, for example, polymerssuch as hydrogenated nitrile, polyacrylate, fluorocarbon, and/orethylene acrylate. However, the material that forms sealing member 24 asdescribed in the present disclosure is not limited in any way. Sealingmember 24 represents a bi-directional lip seal that provides improvedlateral support for accumulator piston 10 within the accumulator bore ofthe housing by reducing or eliminating the rocking motion of accumulatorpiston 10 within the accumulator bore while in use. Thus, the design ofseal member 24 represents an improvement over Original Equipment (OE)seal designs that lack a dual-lip seal.

Because sealing member 24 provides a dual-lip design that covers thesubstantial entirety of side wall 18 of casing 12, a more dynamicsealing mechanism is provided because the side wall 18 of casing 12 isnot exposed. This also results in reduction or elimination of any fluidleakage in the accumulator hydraulic circuit subsystem.

FIG. 2 is a bottom view of accumulator piston 10 of the presentdisclosure. Sealing member 24 can again be seen encircling the outerperiphery of casing 12, covering up side wall 18. As mentioned above,sealing member 24 provides increased stability to accumulator piston 10as well as uniformity in allowing accumulator piston 10 to be able to beplaced within a housing in either an “inverted” orientation, with bottomsurface 16 exposed, or in an upright orientation, with top surface 14exposed (as shown in FIG. 1). The bi-directional nature of accumulatorpiston 10 is discussed in greater detail below with regard to FIG. 7 andFIG. 8.

FIG. 3 and FIG. 4 illustrate accumulator piston 10 of the presentdisclosure in a side perspective view and side view, respectively.Sealing member 24 can be seen clearly covering any exposed surface ofside wall 18 (not shown) of casing 12. Side wall 18 is covered bysealing member 24 to provide increased uniformity of accumulator piston10, and prevent fluid leakage and increased stability when accumulatorpiston 10 is situated within the housing and in use.

FIGS. 5 and 6 are cross-sectional views of accumulator piston 10. Inthese figures, the relationship between sealing member 24 and casing 12can be seen. Sealing member 24 provides a tight seal around the outerperiphery of casing 12, which provides, stability, minimizes leakage,and, advantageously, allows the accumulator piston 10 to be insertedwithin the housing in either in an inverted or upright orientation.

FIG. 7 and FIG. 8 show how sealing member 24 allows accumulator piston10 to be inserted within a housing 26 bi-directionally. This meansaccumulator piston 10 can be inserted within housing 26 in either aninverted fashion, with bottom surface 16 of casing 12 facing up (FIG.7), or in a traditional non-inverted fashion, with the top surface 14 ofcasing 12 facing up.

As explained above, sealing member forms a uniform border around theperiphery of casing 12 such that it makes no difference how accumulatorpiston 10 is inserted within the accumulator bore of housing 26. Forexample, in FIG. 7, accumulator piston 10 is inserted within theaccumulator bore of housing 26 in an inverted position. In thisembodiment, the spring pocket is facing into the housing (and thereforenot show in in FIG. 7). In one embodiment, bottom surface 16 of casing12 of accumulator piston 10 is substantially flush with the surface ofhousing 26. Due to the arrangement of sealing member 24 around the outercircumference of casing 12, i.e., covering side wall 18, a snug seal isformed between accumulator piston 10 and the interior of housing 26,thus minimizing or eliminating fluid leakage and any rocking that mightoccur of accumulator piston 10 while inserted within housing 26.

Referring to FIG. 8, an alternate embodiment is shown where accumulatorpiston 10 is inserted within the accumulator bore of housing 26 in anon-inverted orientation. In this embodiment, piston 10 is insertedwithin the interior of housing 26 with spring pocket 32 facing away fromhousing 26. Again, as in the inverted embodiment shown in FIG. 7,sealing member 24 provides a secure seal between accumulator piston 10and housing 26. In both embodiments, due to the seal between casing 12of accumulator piston 10, fluid leakage is prevented or at leastminimized, and movement or rocking of accumulator piston 10 withinhousing 26 is virtually eliminated. Further, seal member 24 adapts topressure fluctuations in that as pressure upon the accumulator piston 10while it is within housing 26 increases, seal member 24 provides an eventighter and more secure seal. Thus, sealing member 24 imparts a pressureon casing 12 of accumulator piston 10 that is proportional to a pressureimparted on sealing member 24 from, for example, fluids within housing26.

Another feature of seal member 24 is that it allows accumulator piston10 to be inserted within the accumulator bore even if the accumulatorbore is non-concentric. Due to the pliable nature of seal member 24 andits orientation around the outer circumference of casing 12, whichcreates a uniform exposed surface, accumulator piston 10 is able to beinserted and secured within an accumulator bore that is not perfectlycircular or concentric with accumulator piston 10.

Many different embodiments have been disclosed herein, in connectionwith the above description and the drawings. It will be understood thatit would be unduly repetitious and obfuscating to literally describe andillustrate every combination and subcombination of these embodiments.Accordingly, all embodiments can be combined in any way and/orcombination, and the present specification, including the drawings,shall be construed to constitute a complete written description of allcombinations and subcombinations of the embodiments described herein,and of the manner and process of making and using them, and shallsupport claims to any such combination or subcombination.

It will be appreciated by persons skilled in the art that theembodiments described herein are not limited to what has beenparticularly shown and described herein above. In addition, unlessmention was made above to the contrary, it should be noted that all ofthe accompanying drawings are not to scale. A variety of modificationsand variations are possible in light of the above teachings.

1. An accumulator piston configured to be situated within an accumulatorbore of a housing, the accumulator piston comprising: a casingcomprising: a top surface, a bottom surface opposite the top surface,and a side wall situated between the top surface and the bottom surface;a pin guide protruding from the top surface of the casing, the pin guideincluding a centrally disposed aperture, the aperture configured toreceive an elongated pin; and a continuous sealing member completelyencircling the side wall of the casing such that the sealing membercovers any exposed surface of the side wall.
 2. The accumulator pistonof claim 1, wherein the sealing member is configured to preventmisalignment of the accumulator piston within the accumulator bore bymaintaining the casing in a substantially parallel orientation withrespect to the accumulator bore.
 3. The accumulator piston of claim 1,wherein the pin guide is integral with the casing.
 4. The accumulatorpiston of claim 1, wherein the continuous sealing member includes adual-lip design that allows the sealing member to extend over andbeneath the side wall.
 5. The accumulator piston of claim 1, wherein atleast one of the pin guide and the elongated pin is made of hardenedsteel.
 6. The accumulator piston of claim 1, wherein the sealing memberallows the piston to adapt to accumulator bores that are non-concentric.7. The accumulator piston of claim 1, wherein the sealing member is apolymer.
 8. The accumulator piston of claim 7, wherein the polymer is atleast one of hydrogenated nitrile, polyacrylate, fluorocarbon, andethylene acrylate.
 9. The accumulator piston of claim 1, wherein thesealing member imparts a pressure on the casing of the piston that isproportional to a pressure imparted on the sealing member.
 10. Anaccumulator piston configured to be situated within an accumulator boreof a housing for use in automatic vehicle transmissions, the accumulatorpiston comprising: a cylindrical casing comprising: a top surface, abottom surface opposite the top surface, and a side wall situatedbetween the top surface and the bottom surface; a pin guide protrudingfrom the top surface of the cylindrical casing, the pin guide includinga centrally disposed aperture, the bore configured to receive anelongated pin; and a continuous polymer sealing member having a dual-lipdesign that allows the sealing member to completely encircle and extendover and beneath the side wall of the cylindrical casing such that thesealing member covers any exposed surface of the side wall, the sealingmember providing a uniform surface such that the sealing member isconfigured to prevent misalignment of the accumulator piston within theaccumulator bore by maintaining the cylindrical casing in asubstantially parallel orientation with respect to the accumulator bore.